A type of rotary valve commonly used in pneumatic conveying systems for transporting comminuted materials typically consists of a housing having a chamber provided with a cylinder wall, an inlet for receiving comminuted material from a material holding vessel or the like communicating with the housing chamber, and an outlet also communicating with the housing chamber and communicable with a pneumatic conveying line or the like, and a pair of end walls closing the chamber, a shaft journaled in the end walls of the housing, and a rotor mounted on or formed integrally with the shaft within the housing chamber, having a pair of axially spaced shrouds and a plurality of radially projecting vanes between such shrouds providing a plurality of circumferentially spaced pockets adapted to receive material from the inlet, convey it through the rotor chamber and discharge it through the outlet. Since there normally exists a pressure differential across the rotor of such valves, leakage of conveying air and/or material being conveyed is apt to occur in the rotor chamber. To prevent such leakage, there usually is provided an annular packing seal engaging the periphery of each shroud of the rotor and the cylindrical wall of the chamber, a follower plate engaging such annular packing seal and means for urging the follower plate against the packing seal to enhance the sealing action of the packing seal.
In the earlier prior art, such means for urging the follower plate into engagement with the packing seal often has consisted of a number of circumferentially spaced adjustment screws threaded through openings in an adjacent end wall of the housing and engaging the follower plate. A disadvantage of such end seal assemblies utilizing adjustment screws has been that they require a uniform threading of such screws in order to provide a uniform application of force of the follower plate on the annular packing seal. Otherwise, the packing seal engaging the rotor shroud would wear unevenly, requiring frequent replacement.
The problem of applying a nonuniform force on such follower plates by the use of adjustment screws has somewhat been overcome by the use of fluid pressure for urging the follower plate against the packing seal to correspondingly compress the seal against the peripheral portion of the rotor shroud and the adjacent cylindrical wall of the rotor chamber. Examples of such type of end seal assemblies are illustrated and described in U.S. Pat. Nos. 4,915,265, and 4,946,078.
While prior art end seal assemblies for rotary valves utilizing fluid pressure has been an improvement over the use of adjustment screws for displacing the follower plate in such type of valves, such assemblies have not been found to be entirely satisfactorily in providing effective sealing of the rotors. It thus is the principal object of this invention to provide a rotary valve of the type described having an improved end seal which is comparatively simple in design, effective in service and easy to disassemble and reassemble.